PROJECT SUMMARY. Significance. Great progress has been made toward the UNAIDS 90-90-90 goals worldwide, and novel methods for HIV prevention are beginning to decrease the size of the epidemic. However, much work on the HIV continuum of care remains. Racial and ethnic diversity among HIV researchers will be critical in developing new approaches to address the ?10-10-10? gap that currently eludes the best behavioral science conducted to date. Yet, funding rates for underrepresented in medicine/public health (URM) researchers are well below those of white researchers (~15% versus 25%) and only 6% of K career development award applicants have been URM trainees. Approach. In Aim 1, the proposed Fostering Diversity in HIV Research Program will follow Social Cognitive Career Theory and the Mentoring Across Difference framework to train mentors in key skills to successfully support URM trainees. Workshops will be held annually with additional quarterly sessions. In Aim 2, the program will provide structured research mentorship exclusively to URM trainees to address the HIV continuum of care. Trainees will be identified through residency and post-doctoral fellowship programs at Massachusetts General Hospital (Departments of Medicine, Infectious Disease, Psychiatry, Obstetrics/Gynecology) and master?s degree and PhD programs at the Harvard T. H. Chan School of Public Health (Departments of Behavioral and Social Science, Global Health and Population, Epidemiology, Immunology and Infectious Diseases); recruitment will also involve active outreach efforts. Trainees will receive formal didactics on the HIV continuum of care and career development, focusing on issues particularly relevant for URM trainees (e.g., implicit bias). Mentors will support URM trainees in gaining knowledge about behavioral HIV research, as well as provide the hands-on technical and professional skills needed to develop successful research careers. All activities will be tailored to the needs of URMs and each individual?s stage of training. Research will address the following areas of the HIV continuum of care both domestically and globally: PrEP delivery and adherence; HIV testing and outreach; linkage, retention in care, and ART adherence; chronic care and complications of treated HIV; maternal health and perinatal transmission. Primary outcomes of the program will be HIV research mentors with the necessary mentoring competencies to successfully support URM trainees, as well as high quality, satisfying, and impactful mentorship of URM trainees who achieve core research competencies. Other outcomes include trainee scholarship (i.e., manuscripts and grants), progression of trainees through the academic research pipeline, and fidelity of program implementation. Innovation. The Fostering Diversity in HIV Research Program is innovative in its 1) targeted training of mentors to effective support URM trainees, 2) focus on the transition periods when many trainees leave academic research, 3) creation of a broad-based Community of Practice among URM trainees, and 4) interdisciplinary focus, fostering cross-collaboration and team science.